Mold on once-turned bowls

[Holmes Anderson]

I have been making some once-turned bowls from a cherry tree that was dormant and healthy when cut. Mold spots form on the bowls within about 24-48 hours of turning. Not sure about the MC but it is probably high because the wood has been in below freezing temps and is being turned while still frozen so most of the moisture that was in the standing tree is basically locked in until the bowls warm up during drying. The shop temp is about 50 degrees F and the RH is usually low. The mold spots are troublesome because they run too deep to easily be sanded away. Not sure what would be the simplest solution. Basic kiln? Bleach or boric acid wash? Just rough-turn and deal with the mold later during a second turning?

Bowls being dried on a shelf 15 feet from an exterior door without anything to slow drying. Mold forms even if they are not stacked. Very little mold forms on rough-outs sealed with Anchorseal and stacked nearby so I assume the mold spores are in the shop.

 

[Don Wattenhofer]

I have done many pieces from green cherry and have never had a problem like that and since I detest drying checks in a turned piece I try to turn as soon as possible. When I do a once turned piece I always try for as consistently thin wall as possible and they will then dry within a few days. The bowl in the picture shows what you can do if you get it thin enough such that it will distort rather then crack. My shop is kept at least 50 degrees F and when I am in there towork I fire up a wood burning stove and bring it up to about 65 to 68 F.

 

[Randy Anderson]

Holmes, I've turned a lot of black Cherry but don't recall mold spots being an issue on once turned or twice turned. You have any pics to share? You sure they're not metal stain spots from your tools?

 

[Holmes Anderson]

 

[Randy Anderson]

Not sure but that could well be metal staining. Certainly looks like it in the circle where your live center was in place. Have you doused it good with lemon juice? I often spray entire pieces down if I start to see any signs of it. Rub it on, all around, let it sit, spray some more, etc. Miracle solution to the problem if that's what it is. I spray my hands as well after turning walnut and other woods that stain my hands.

 

[hockenbery]

I usually rinse my once turned bowls in the sink before I start to dry them
It adds some moisture back to the endgrain and gets any dust off the bowl

 

[robo hippy]

I am wondering if those are metal stains rather than mold. I learned long ago to wipe off my tools after sharpening, and my hands, before going back to the wood. Any metal dust on hands and/or tool will cause spots and finger prints. concentrated lemon juice removes them instantly when the wood is still fresh. Much slower when the wood has dried, which takes a week at most in my shop.

robo hippy

 

[Holmes Anderson]

Thanks, I will try the lemon juice. I would much rather it is metal stains than mold. I think some of the marks even look suspiciously like fingerprints.

 

[Brian Gustin]

Agree with the others - Looks like Tannins in the wood reacting with iron/metal (Oak will do that too) Do you happen to be sharpening tools on grinder nearby? Dust from grinding can get in the air and settle on the wood , resulting in stains like that. It isn't just metal either- you can get that black staining from sweating on even dry wood (salts and minerals in sweat will also react with the Tannins in the wood)

 

[Marc Banka]

I recently got a section of a cherry tree, living and healthy, freshly cut. I’ve been rough turning some of it, but then do some once turned pieces (calabash style bowls), just because I want to have a few finished pieces from this gorgeous wood. (I don’t often get Cherry)
The rough cut, anchorsealed blanks have no spots. The once turned bowls get the staining . My wont is to wrap any, in progress, once turned bowls tightly in plastic if I can’t finish in one sitting. The next day spots appear and the greying accumulates at the endgrain areas.
I’ve found that if I wash the partially done piece with Barkeeper’s friend, it stops the spots, clears a lot of it away and brightens the cherry, especially at the endgrain where it was looking dirty. I washed and rinsed well, and continued my work.

 

[Holmes Anderson]

Just following up after trying some of the suggested solutions, the staining was from the tool steel as people suggested. The lemon juice solved the problem. Barkeeper's Friend was also effective. The grinder is 4 feet directly across from the lathe but it seems that most of the powdered metal is created by contact between the tools and the frozen wood. A paste of powdered metal and wood builds up just under the cutting edge of the tools and discolors both the tools and bowls. I now bother to wipe it off frequently. I think the frozen wood is more abrasive than wood that isn't frozen.

 

[Ric Williams]

I've had fresh cut choke cherry, cut into bowl blanks then immediately sealed in paraffin wax, grow mold under the wax after a few days. I figured that there's moisture and sugars in the wood, so it's a perfect environment to grow mold samples.

 

[John K Jordan]

I've had fresh cut choke cherry, cut into bowl blanks then immediately sealed in paraffin wax, grow mold under the wax after a few days. I figured that there's moisture and sugars in the wood, so it's a perfect environment to grow mold samples.

What time of year was it? Some species do better with color when it's cold, even freezing. (When I ordered blades for my Woodmizer they asked me if I wanted them for frozen wood.)

JKJ

 

[Ric Williams]

What time of year was it? Some species do better with color when it's cold, even freezing. (When I ordered blades for my Woodmizer they asked me if I wanted them for frozen wood.)

JKJ

In my case it was late spring, so the wood was definitely not frozen. The sap wood was affected much more than the heart wood, but I assume there's more sugar in the sap wood, so it's not surprising. Not sure what you mean in referring to the color though.

 

[Don Stephan]

Just following up after trying some of the suggested solutions, the staining was from the tool steel as people suggested. The lemon juice solved the problem. Barkeeper's Friend was also effective. The grinder is 4 feet directly across from the lathe but it seems that most of the powdered metal is created by contact between the tools and the frozen wood. A paste of powdered metal and wood builds up just under the cutting edge of the tools and discolors both the tools and bowls. I now bother to wipe it off frequently. I think the frozen wood is more abrasive than wood that isn't frozen.

My experience making once turned bowls, shavings (likely including metal dust) can accumulate in the gouge flute. Wiping the flute clean with my fingers apparently transferred some metal dust to my finger tips, and after turning the bowl around or removing from the chuck black smears would be on the wood. Now I keep a glue brush on the headstock which I use to wipe out the flute, and the black smears don't appear.

 

[Don Wattenhofer]

In my case it was late spring, so the wood was definitely not frozen. The sap wood was affected much more than the heart wood, but I assume there's more sugar in the sap wood, so it's not surprising. Not sure what you mean in referring to the color though.

That was the worst possible time to cut a tree down when the sap is running. A better way to use the wood is to leave it in larger pieces then cut into a turning blank when you are ready to turn one, then coat with Anchorseal on the end grain areas or better yet put them in a brown paper bag and weigh them keeping a record of the weight until it ceases to change.

 

[robo hippy]

I prefer to get my madrone logs when the spring sap first starts to run, which is end of February or early March. Mostly I get fewer cracks in the madrone that way than if I get an early summer log. Madrone warps to no rhyme or reason, and cored sets can all warp differently. Madrone has to be once turned or boiled, and I don't like the boiling because it muddles the colors together.

robo hippy

 

[Ric Williams]

That was the worst possible time to cut a tree down when the sap is running. A better way to use the wood is to leave it in larger pieces then cut into a turning blank when you are ready to turn one, then coat with Anchorseal on the end grain areas or better yet put them in a brown paper bag and weigh them keeping a record of the weight until it ceases to change.

That was just when I processed it. We have about 5 1/2 acres of woods and I just harvest stuff that's already on the ground. I leave them in 4-6 ft logs and cut them down to blanks when I process a log, then seal the blanks with Anchorseal. I usually rough turn them, reseal them, then put them in paper bags and weigh them. When the weight loss slows down, I take them out of the bags and let them air dry until the weight stabilizes. If a blank isn't rough turned right away, it's sealed, left to air dry and weighed until it stabilizes. At this point I've got more cherry, red oak, hickory, elm, mulberry, cedar and box elder than I'll use in the rest of my lift time. Unfortunately, we don't have any walnut or maple in the woods, but there's a huge multi trunk silver maple in the yard that's getting old. If any of that comes down, I'll definitely harvest it.